[Scribus] CMYK image processing

[Craig Ringer]

On Mon, Mar 20, 2006 at 12:31:03AM +0100, Helmut Wollmersdorfer wrote:
> Craig Ringer wrote:
> 
> > Ignorance is relative. It's true that some GIMP folks haven't recognised
> > the need for CMYK etc, but others certainly do, and I think
> > understanding is growing (of course, CMYK is becoming less important at
> > the same time due to better colour management and so on - they make the
> > IMO valid point that really CMYK should be the RIPs problem).
> 
> The short answer is:
> You need CMYK, if your print shop wants it, or if somebody sends it to you.

Well, you don't need CMYK support in your raster graphics app if your
print shop wants a CMYK PDF. Scribus can - and does - convert RGB
graphics to CMYK according to the embedded or configured input and
output profiles. This is done at PDF export time, and doesn't need any
CMYK support in a graphics app.

If someone sends you CMYK artwork, you should be able to just include
it. Again, little need to involve the GIMP - especially since Scribus
can do any image cropping, rotation, downsampling, and so on that is
required.

You need CMYK support in your graphics app if:
	- You're working without colour management (bad idea!) and want
	  to try to manually adjust the input images.
	- You're attempting to manually adjust an image after converting
	  to CMYK, perhaps trying to exploit parts of the CMYK gamut not
	  available in the RGB space. Since you can't see the results
	  this is a rather unusual thing to ever need to do - most of
	  the time, colour managed conversions of RGB to CMYK will do a
	  better job than you can. Ask Peter or Marti Maria if you don't
	  believe me (I never used to believe it, but now I've seen the
	  results!). There will be a copy of a presentation by Marti
	  on the Scribus site soon that gives a great explanation of
	  colour management, including explaining how the Perceptual
	  rendering intent helps exploit the full gamut of the target
	  during conversions (with some downsides).
	- You want to alter CMYK artwork sent to you, and the sender
	  can't supply you a (preferably tagged) RGB original.

After speaking with Marti Maria at LGM, I'm actually now going to be
going to the printers I use at the POST Newspapers and talking to them
about using us as a trial customer for a colour managed workflow. We
currently use the old-style CMYK preconversion (based on Photoshop
profiles, with artwork output untouched through Quark) approach, but are
upgrading to more modern workstations that'll do colour management
sensibly. My point is that I'm not just fluffing randomly - I intend to
act on my own words here and get rid of manual CMYK image management at
my employer.

-- 
Craig Ringer
GPG Key Fingerprint: AF1C ABFE 7E64 E9C8 FC27  C16E D3CE CDC0 0E93 380D